This invention relates generally to a disc brake operating mechanism and particularly to a mechanism for a disc brake of a truck.
Braking systems of heavy trucks generally use air under pressure as an operating medium. Typically, large air actuators have a mechanical output which applies brake pads to a brake rotor via a lever mechanism. The lever mechanism includes an operating shaft pivotable about an axis to urge one or more tappets against a brake pad via a cam surface. The operating shaft has a lever arm acted upon by the air actuator and may include another generally shorter arm to actuate a wear adjuster. For larger brake pads, twin tappets are provided to optimize pressure distribution on a brake pad backplate.
Typically, a lever mechanism will include an operating shaft extending on a pivot axis on either side of a brake actuator lever. Bearings (usually needle rollers) are provided on each side of the brake actuator lever to resist brake application force and to permit the operating shaft to pivot freely. Twin bearings obviate twisting and end loads on the operating shaft. Typically, the bearings provided on each side of the brake actuator lever sit in saddle components fitted into a brake housing. The saddle components often provide axial retention of the bearing arrangements. The addition of saddle components increases part count, complexity of assembly and cost.
For smaller brake pads, a single tappet is sufficient, but nevertheless twin bearings are provided. This arrangement adds to the cost and weight of the brake, and also results in problems in packaging the components within a smaller brake envelope because space at an inboard side of the brake rotor is limited.
A solution to these problems which permits easier packaging, yet allows both weight and cost to be reduced, is needed.